Gear wrenches, also known as off-set drivers or nut runners, are well known in the industry and typically are used for driving threaded fasteners in height-limited environments (e.g., where a threaded stud is positioned directly adjacent to a flange) or alternately where the end of an elongated tube or pipe line is secured with a threaded fastener. To provide access to the threaded fastener, the gear wrench is provided with a slotted socket gear which readily permits placement of the gear wrench onto the threaded fastener.
For example, U.S. Pat. No. 3,620,105 discloses such an off-set driver in which a socket gear is rotatably supported within a driver housing which is provided with a slot. A complementary slot formed in the socket gear is aligned with the slot formed in the driver housing such that the driver may be applied laterally to the nut without requiring axial shifting of the nut and the socket, thereby enabling engagement of the gear wrench onto a tube nut in a clearance limited environment. After performing a tightening operation, the gear wrench is removed from the nut. However, the slots formed in the socket gear and the housing must be realigned to enable removal of the gear wrench from the threaded fastener or tubing. In this regard, the gear wrench is driven in a reverse direction until the complementary slots are aligned.
However, obtaining precise alignment of the slots formed in the socket gear and gear wrench housing can be difficult and time consuming when no means for achieving alignment is employed. More specifically, precise manual control of the gear wrench may at times be difficult such that precise alignment is not achieved.
Various means for achieving alignment have also been developed. In this regard, U.S. Pat. Nos. 5,460,062 and 5,544,553 disclose a gear wrench in which a pin engages a cut out section of the drive gear in order to align the driving gear, and hence the socket gear, in an appropriate position when the slot of the socket gear is aligned with the opening in the housing. Alternately, as disclosed in U.S. Pat. No. 5,339,710, a pivoting stop arm may be utilized to engage a detent formed in the drive cam gear to place the slot in alignment with the housing. Many of these methods utilize a "hard stop" positioning mechanism which has the disadvantage of overly stressing the drive gear when the positioning mechanism engages. Repeated use of such a gear wrench results in damage and possibly failure of the drive gear assembly. Furthermore, a phenomenon referred to as "bounce back" may occur in which the sudden engagement of the hard stop causes the socket gear to rotate slightly forwardly, thereby misaligning the socket gear slot and the gear housing slot.
In an effort to overcome these disadvantages, manufacturers have employed gear wrenches which utilize a soft reverse motor, whereby the rearward driving torque is substantially less than the forward driving torque. More specifically, the torque generated by the gear wrench in a reverse direction is substantially less than the torque generated in the forward direction. However, the incorporation of a soft reverse feature into the drive head adds cost and complexity to the gear wrench motor. Furthermore, the soft reverse motor limits the use of the drive head to tube nut applications such that the drive head cannot be used for torque check or disassembly functions which require driving torque in a reverse direction.